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# Amoxicillin + clavulanic acid

Amoxicillin shielded by clavulanic acid, which blocks β-lactamases; an oral antibiotic for otitis, sinusitis, pneumonia and skin infections.

Updated 2026-11-01

- Class: [Beta-lactams](https://durgical.com/en/pharmacology/classes/beta-lactams/)
- Enzyme: Bacterial PBPs (amoxicillin) and β-lactamases (clavulanic acid)
- ATC code: J01CR02
- WHO Model List of Essential Medicines

Also called: co-amoxiclav, amoxicillin–clavulanate

✂**Bacterial PBPs (amoxicillin) and β-lactamases (clavulanic acid)**Amoxicillin + clavulanic acid

ⓘ The figure shows clavulanic acid in the active site of the extended-spectrum β-lactamase TLA-1 (S70G mutant, without the catalytic serine, so the molecule stays intact); amoxicillin acts on the PBPs as on its own page.

**Target in 3D:** Bacterial PBPs (amoxicillin) and β-lactamases (clavulanic acid). PDB structure 6PQ8 (RCSB PDB, public domain). [View the structure at RCSB PDB](https://www.rcsb.org/structure/6PQ8) · Drag to rotate · pinch to zoom

## Mechanism of action

Amoxicillin acylates the penicillin-binding proteins (PBPs) and stops peptidoglycan cross-linking. Many bacteria (Haemophilus influenzae, Moraxella catarrhalis, Staphylococcus aureus, anaerobes, enteric gram-negatives) destroy it with β-lactamases. Clavulanic acid has almost no antibacterial action of its own but is a 'suicide' inhibitor: the β-lactamase opens it and is irreversibly inactivated, so amoxicillin reaches its PBPs intact.

- The bacterium secretes β-lactamase to defend itself
- Clavulanic acid binds the β-lactamase and inactivates it
- Amoxicillin, now protected, acylates the PBPs
- Without cross-links the wall gives way and the bacterium lyses

## Pharmacokinetics

**Absorption**
Both are well absorbed by mouth; taking it at the start of a meal improves clavulanate absorption and stomach tolerance.

**Elimination**
Amoxicillin leaves mostly unchanged in the urine; clavulanate by the urine and by metabolism.

**Half-life**
About 1.3 hours for amoxicillin and 1 hour for clavulanic acid.

## Indications

- Acute otitis media due to β-lactamase-producing bacteria. [Acute otitis media →](https://durgical.com/en/conditions/acute-otitis-media/)
- Acute bacterial sinusitis. [Acute rhinosinusitis →](https://durgical.com/en/conditions/acute-rhinosinusitis/)
- Lower respiratory tract infections such as community-acquired pneumonia. [Community-acquired pneumonia →](https://durgical.com/en/conditions/community-acquired-pneumonia/)
- Skin and soft-tissue infections. [Cellulitis of the leg →](https://durgical.com/en/conditions/cellulitis-of-the-leg/)
- Urinary tract infections by susceptible strains. [Urinary tract infection (acute cystitis) →](https://durgical.com/en/conditions/urinary-tract-infection/)

## Adverse effects

### Common

- Diarrhoea (more often than with amoxicillin alone), nausea and vomiting
- Rash; very common if the patient has infectious mononucleosis
- Vaginal or oral candidiasis

### Serious (rare, important)

- Hepatitis and cholestatic jaundice, usually reversible but sometimes severe; they may appear after the course ends
- Anaphylaxis
- Severe skin reactions (Stevens–Johnson, toxic epidermal necrolysis, DRESS, acute generalised exanthematous pustulosis)
- Clostridioides difficile diarrhoea, from mild to severe colitis

## Contraindications

- History of a serious hypersensitivity reaction (anaphylaxis, Stevens–Johnson syndrome) to any penicillin or other β-lactam
- Previous cholestatic jaundice or liver dysfunction linked to amoxicillin + clavulanic acid

## Key interactions

**Probenecid**
Reduces tubular secretion: higher and longer-lasting β-lactam levels.

**Allopurinol**
Raises the rate of rash with aminopenicillins.

**Oral anticoagulants (warfarin)**
May prolong the prothrombin time; the INR is monitored.

## What is monitored

- Clinical response in the first days
- Liver tests if there is prior liver disease or jaundice, dark urine or itching appear
- INR if the patient takes warfarin

## Administration and safety

- Oral; given at the start of a meal to improve stomach tolerance.
- Presentations are not interchangeable: the clavulanate ratio differs, and two tablets do not equal one stronger tablet.
- Do not confuse it with plain amoxicillin: the names look alike and the spectrum is not the same.

## Nursing care

- Before the first dose: ask about allergy to penicillins, cephalosporins and other β-lactams, and what the reaction was.
- After the first dose, watch for hives, wheeze, low blood pressure or swelling of lips and tongue, with anaphylaxis equipment at hand.
- Watch for jaundice, dark urine, pale stools or itching, also after the course ends.
- Teach the patient to report watery or bloody diarrhoea, even weeks after the course ends.
- Stress completing the prescribed course even if symptoms improve.

## Pregnancy and breastfeeding

Decades of use have not shown more birth defects; in preterm prelabour rupture of membranes it has been linked to more neonatal necrotising enterocolitis.

## Memory aid

Clavulanate is the 'bodyguard' that takes the β-lactamase's bullet so amoxicillin reaches the wall. The bodyguard's fee: more diarrhoea and, rarely, a cholestatic liver.

## Test yourself

Think of the answer, then tap the question to see it.

## Why is clavulanic acid called a 'suicide' inhibitor?

Because the β-lactamase takes it as a substrate, opens its ring and remains irreversibly bound to it: the enzyme inactivates itself while trying to destroy it.

## Which serious adverse effect rules out using amoxicillin + clavulanic acid again?

Cholestatic jaundice or liver dysfunction linked to a previous course of the combination.

## What extra spectrum does clavulanate add to amoxicillin?

It covers β-lactamase producers such as H. influenzae, M. catarrhalis, methicillin-susceptible S. aureus and many anaerobes.

## Does clavulanate help against methicillin-resistant Staphylococcus aureus (MRSA)?

No. MRSA resists through PBP2a, a low-affinity PBP, not through a β-lactamase; blocking the β-lactamase does not fix that.

[Add to my cards (4)](https://durgical.app/estudiar/?add=/en/pharmacology/amoxicillin-clavulanic-acid/)

## Related drugs

- [Amoxicillin](https://durgical.com/en/pharmacology/amoxicillin/)
- [Ampicillin + sulbactam](https://durgical.com/en/pharmacology/ampicillin-sulbactam/)
- [Piperacillin + tazobactam](https://durgical.com/en/pharmacology/piperacillin-tazobactam/)

## Related conditions

- [Acute otitis media](https://durgical.com/en/conditions/acute-otitis-media/)
- [Acute rhinosinusitis](https://durgical.com/en/conditions/acute-rhinosinusitis/)
- [Community-acquired pneumonia](https://durgical.com/en/conditions/community-acquired-pneumonia/)
- [Cellulitis of the leg](https://durgical.com/en/conditions/cellulitis-of-the-leg/)
- [Urinary tract infection (acute cystitis)](https://durgical.com/en/conditions/urinary-tract-infection/)

[← Back to the class: Beta-lactams](https://durgical.com/en/pharmacology/classes/beta-lactams/)

Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.

Sources: [Amoxicillin and Clavulanic Acid: MedlinePlus Drug Information](https://medlineplus.gov/druginfo/meds/a685024.html) (MedlinePlus (U.S. National Library of Medicine), 2026); [DailyMed - AMOXICILLIN AND CLAVULANATE POTASSIUM tablet, film coated](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=80bef3fd-4f6f-4190-8865-9ac46c8947a3) (DailyMed (U.S. National Library of Medicine), 2026); [RCSB PDB - 6PQ8: Crystal structure of TLA-1 S70G extended spectrum Beta-lactamase in complex with clavulanic acid](https://www.rcsb.org/structure/6PQ8) (RCSB Protein Data Bank, 2026); Farmacología básica y clínica (Katzung), cap. 43 (McGraw Hill, 2025).

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Representative model, for educational purposes only.

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License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/pharmacology/amoxicillin-clavulanic-acid/